Weight loss: Feel full on fewer calories

Feel full on fewer calories? It might sound like another gimmick for weight loss, but it's not. The concept of energy density really can help with weight loss. In fact, well-planned weight-loss diets, such as the Mayo Clinic Diet, use the concept of energy density to help you lose weight and keep it off long term.

Weight loss with more food, fewer calories

Simply put, energy density is the number of calories (energy) in a specific amount of food. High energy density means that there are a lot of calories in a little food. Low energy density means there are few calories in a lot of food.

When you're striving for weight loss, the goal is to eat low-energy-dense foods. That is, you want to eat a greater volume of food that's lower in calories. This helps you feel fuller on fewer calories. Here's a quick example with raisins and grapes. Raisins have a high energy density -- 1 cup of raisins has about 434 calories. Grapes have a low energy density -- 1 cup of grapes has about 82 calories.

The keys to energy density and weight loss

Three main factors play a role in what makes food high or low in energy density:

Water. Fruits and vegetables are generally high in water content, which provides volume and weight but not calories. That's why they're low-energy-dense foods. Grapefruit, for example, is about 90 percent water. Half a grapefruit has just 37 calories. Raw, fresh carrots are about 88 percent water. A medium carrot has only about 25 calories.

Fiber. High-fiber foods not only provide volume, but also take longer to digest, making you feel full longer on fewer calories. Vegetables, fruits and whole grains all contain fiber. Popcorn is a good example of a high-volume, low-calorie whole grain. One cup of air-popped popcorn has about 30 calories.

Fat. Fat is high in energy density. One pat of butter, for example, contains almost the same number of calories as 2 cups of raw broccoli. Foods that contain fat naturally, such as dairy products and various meats, or foods with added fats are higher in calories than are their leaner or lower fat counterparts.

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